1. Field of the Invention
The present invention relates to a production method for an active matrix substrate, in which a contact hole is formed in an insulating layer to provide electrical connection, in a semiconductor device or a liquid crystal display, between an electrode, wiring, or terminal (hereafter, referred to simply as the “electrode”) and an upper electrode arranged thereabove with the insulating layer interposed therebetween. The present invention particularly relates to a production method for an active matrix substrate suitable for use when the electrode is composed of a Cr film or Cr alloy film (hereafter, referred to simply as the “Cr film”), or an Al film or Al alloy film (hereafter, referred to simply as the “Al film”).
2. Description of the Related Art
In general, dry etching of RIE (Reactive Ion Etching) type using fluorine gas such as CF4 or SF6 alone is performed when a plurality of contact holes are formed in a silicon insulating layer by a one-mask process to reach a plurality of electrodes formed of a Cr or Al film and located at different depth positions in the silicon insulating layer. This type of contact hole forming method is disclosed in Japanese Laid-Open Patent Publication No. 2001-102362 (Patent Document 1) and No. 2001-308182 (Patent Document 2), for example.
FIG. 1 is a diagram showing a contact hole forming method according to a related art similar to those disclosed in Patent Documents 1 and 2.
Referring to FIG. 1, a first electrode 62 formed of a Cr film and a second electrode 64 also formed of a Cr film are located at different depth positions on and above a glass substrate 61. A silicon insulating layer 63 and another silicon insulating layer 65 are arranged on the first electrode 62. The silicon insulating layer 65 is located on the second electrode 64. RIE dry etching using SF6 gas alone is performed to form contact holes in the silicon insulating layers 63 and 65 so as to reach the first electrode 62 and the second electrode 64, respectively, through a resist layer 66.
In contrast, when a contact hole is formed in a silicon insulating layer to reach an electrode formed of an Al film or the like and located within a silicon insulating layer, RIE dry etching using mixed gas of CHF3 and CF4 is performed. This type of contact hole forming method is, for example, disclosed in Japanese Laid-Open Patent Publication No. H07-37866 (Patent Document 3) and WO 00/039845(Patent Document 4).